Reproductive and transgenerational toxicity of bisphenol S exposure in pregnant rats: Insights into hormonal imbalance and steroid biosynthesis pathway disruption.

Bisphenol S (BPS) is an alternative chemical to bisphenol A commonly used in food packaging materials. It raises concerns due to potential adverse effects on human health. However, limited evidence exists regarding reproductive toxicity from BPS exposure, and the mechanism of associated transgenerational toxicity remains unclear. In this study, pregnant SD rats were exposed to two different doses of BPS (0.05 or 20 mg/kg) from GD6 to PND21. The objective was to investigate reproductive and transmissible toxicity induced by BPS, explore endocrine effects, and uncover potential underlying mechanisms in rats. Perinatal exposure to BPS in the F0 generation significantly decreased the rate of body weight, ovarian organ coefficient, and growth and development of the F1 generation. Notably, these changes included abnormal increases in body weight and length, estrous cycle disruption, and embryonic dysplasia in F1. 4D-DIA proteomic and PRM analyses revealed that exposure to 20 mg/kg group significantly altered the expression of proteins, such as Lhcgr and Akr1c3, within the steroid biosynthetic pathway. This led to elevated levels of FSH and LH in the blood. The hypothalamic-pituitary-ovarian (HPO) axis, responsible for promoting fertility through the cyclic secretion of gonadotropins and steroid hormones, was affected. RT-qPCR and Western blot results demonstrated that the expression of GnRH in the hypothalamus was decreased, the GnRHR in the pituitary gland was decreased, and the expression of FSHß and LHß in the pituitary gland was increased. Overall, BPS exposure disrupts the HPO axis, hormone levels, and steroid biosynthesis in the ovaries, affecting offspring development and fertility. This study provides new insights into the potential effects of BPS exposure on the reproductive function of the body and its relevant mechanisms of action.

Isothiazolinone Disrupts Reproductive Endocrinology by Targeting the G-Protein-Coupled Receptor Signaling.

The unintended exposure of humans and animals to isothiazolinones has led to an increasing concern regarding their health hazards. Isothiazolinones were previously found to disrupt reproductive endocrine homeostasis. However, the long-term reproductive toxicity and underlying mechanism remain unclear. In this study, life-cycle exposure of medaka to dichlorocthylisothiazolinone (DCOIT), a representative isothiazolinone, significantly stimulated the gonadotropin releasing hormone receptor (GnRHR)-mediated synthesis of follicle stimulating hormone and luteinizing hormone in the brain. Chem-Seq and proteome analyses revealed disturbances in the G-protein-coupled receptor, MAPK, and Ca2+ signaling cascades by DCOIT. The G protein αi subunit was identified as the binding target of DCOIT. Gαi bound by DCOIT had an enhanced affinity for the mitochondrial calcium uniporter, consequently changing Ca2+ subcellular compartmentalization. Stimulation of Ca2+ release from the endoplasmic reticulum and blockage of Ca2+ uptake into the mitochondria resulted in a considerably higher cytoplasmic Ca2+ concentration, which then activated the phosphorylation of MEK and ERK to dysregulate hormone synthesis. Overall, by comprehensively integrating in vivo, ex vivo, in silico, and in vitro evidence, this study proposes a new mode of endocrine disrupting toxicity based on isothiazolinones, which is expected to aid the risk assessment of the chemical library and favor the mechanism-driven design of safer alternatives.

Isothiazolinone dysregulates the pattern of miRNA secretion: Endocrine implications for neurogenesis.

Isothiazolinones are extensively used as preservatives and disinfectants in personal care products and household items. The unintended exposure of humans and animals to isothiazolinones has led to increasing concerns about their health hazards. The compound 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), a representative isothiazolinone, can simultaneously induce endocrine disruption and neurotoxicity. However, the underlying mechanisms and linkages remain unclear. Our purpose was to elucidate the role of miRNAs as the signaling communicator during the crosstalk between endocrine and nervous systems in response to DCOIT stress. H295R cells were exposed to DCOIT, after which the alterations in intracellular miRNA composition, exosome secretory machinery, and extracellular miRNA composition were examined. Then, a PC12 cell line of neuronal differentiation potential was cultured with the extract of extracellular miRNAs from DCOIT-exposed H295R cell media to explore the functional implications in neurogenesis. The results showed that DCOIT exposure resulted in 349 differentially expressed miRNAs (DEMs) in H295R cells, which were closely related to the regulation of multiple endocrine pathways. In the media of H295R cells exposed to DCOIT, 66 DEMs were identified, showing distinct compositions compared to intracellular DEMs with only 2 common DEMs (e.g., novel-m0541-5p of inverse changes in the cell and medium). Functional annotation showed that extracellular DEMs were not only associated with sex endocrine synchronization, but were also implicated in nervous system development, morphogenesis, and tumor. Incubating PC12 cells with the extracellular exosomes (containing miRNAs) from DCOIT-exposed H295R cells significantly increased the neurite growth, promoted neuronal differentiation, and shaped the transcriptomic fingerprint, implying that miRNAs may communicate transduction of toxic information of DCOIT in endocrine system to neurons. Overall, the present findings provide novel insight into the endocrine disrupting and neural toxicity of DCOIT. The miRNAs have the potential to serve as the epigenetic mechanism of systems toxicology.

Evaluation and comparison of the mitochondrial and developmental toxicity of three strobilurins in zebrafish embryo/larvae.

Strobilurin fungicides have been frequently detected in aquatic environments and can induce mitochondrial toxicity to non-target aquatic organisms. However, the derived toxicity and subsequent mechanisms related to their adverse effects are not fully elucidated. In the present study, we compared the mitochondrial and developmental toxicity of azoxystrobin, pyraclostrobin, and trifloxystrobin using zebrafish embryo/larvae. The results showed that all three strobilurins inhibited mitochondrial and non-mitochondrial respiration (the potency is pyraclostrobin ≈ trifloxystrobin > azoxystrobin). Behavioral changes indicated that sublethal doses of pyraclostrobin and azoxystrobin caused hyperactivity of zebrafish larvae in dark cycles, whereas trifloxystrobin resulted in hypoactivity of zebrafish larvae. In addition, pyraclostrobin exposure impaired the inflation of swim bladder, and caused down-regulation of annexin A5 (anxa5) mRNA levels, and up-regulated transcript levels of pre-B-cell leukemia homeobox 1a (pbx1a); conversely, azoxystrobin and trifloxystrobin did not cause detectable effects with swim bladder inflation. Molecular docking results indicated that azoxystrobin had higher interacting potency with iodotyrosine deiodinase (IYD), prolactin receptor (PRLR), antagonistic conformation of thyroid hormone receptor ß (TRß) and glucocorticoid receptor (GR) compared to pyraclostrobin and trifloxystrobin; pyraclostrobin and azoxystrobin were more likely to interact with the antagonistic conformation of TRß and GR, respectively. These results may partially explain the different effects observed in behavior and swim bladder inflation, and also point to potential endocrine disruption induced by these strobilurins. Taken together, our study revealed that all three strobilurins alter mitochondrial bioenergetics and cause developmental toxicity. However, the toxic phenotypes and underlying mechanisms of each chemical may differ, and this requires further investigation. Pyraclostrobin showed higher mitochondrial toxicity at lethal doses and higher developmental toxicity at sublethal doses compared to the two other strobilurins tested. These results provide novel information for toxicological study as well as risk assessment of strobilurin fungicides.

Unexpected Observations: Probiotic Administration Greatly Aggravates the Reproductive Toxicity of Perfluorobutanesulfonate in Zebrafish.

The present study exposed adult zebrafish to 0, 10, and 100 µg/L perfluorobutanesulfonate (PFBS) with or without dietary supplement of probiotic Lactobacillus rhamnosus. Interaction between probiotic and PFBS on sex endocrine and reproduction was investigated. It was striking to find that PFBS and probiotic coexposures almost ceased the fecundity, which was accompanied by disturbances in sex hormones and oocyte maturation in females. In contrast, probiotic additive efficiently antagonized the estrogenic activity of PFBS in males. For the first time, this study reported that probiotic heavily depended on sex to modulate the endocrine disruption and reproductive toxicity of aquatic pollutants.

Evaluation and mechanistic study of chlordecone-induced thyroid disruption: Based on in vivo, in vitro and in silico assays.

The present study aimed to evaluate the thyroid-disrupting potency of chlordecone, and reveal the underlying mechanism. In the in vivo assays, rare minnow embryos were exposed to 0, 0.01, 0.1, 1 and 10 µg·L-1 chlordecone until sexually mature. The results showed decreased T4 but increased T3 concentrations in plasma, upregulated mRNA levels of thyrotropin-releasing hormone receptor (trhr) and sodium-iodide symporter (nis) in the brain, and transthyretin (ttr), thyroid hormone receptor α (trα) and deiodinase enzymes (dio1 and dio2) in the liver of adult fish. In the in vitro assays, single chlordecone treatments promoted growth hormone (GH) and prolactin (PRL) secretion in GH3 cells. Transcription of thyroid receptor (trß) was inhibited, but this is not likely responsible for chlordecone-induced GH secretion and altered transcription. When co-treated with T3, chlordecone acted independently of the effect of T3 on GH secretion; chlordecone-induced GH/PRL secretion and mRNA expression were further promoted when co-treated with E2, but inhibited when co-treated with ICI, indicating an important role for estrogen receptors (ERs) in chlordecone-induced changes in GH3 cells. Furthermore, in silico prediction suggested no stable interactions between chlordecone and thyroid hormone-related proteins, as well as a regulatory role for ERs in thyroid systems. Overall, our results indicated that chlordecone may have adverse effects on thyroid systems upon long-term exposure. However, rather of TRs, ERs may be responsible for thyroid disruption following chlordecone exposure.

Exposure to cadmium causes inhibition of otolith development and behavioral impairment in zebrafish larvae.

Otolith consisting largely of calcium carbonate, fibrous and proteins, is vital for maintaining body balance and/or hearing of fish. The formation of otolith involves Ca2+ transport and deposition. In the present study, we investigated the effects of Cd2+ on otoliths development by using zebrafish embryos as model. The results showed that exposure to Cd2+ inhibited the utricular and saccular otoliths growth, indicated by reduced lateral areas. Swimming speeds were reduced and a losing balance control was observed in Cd2+ exposed larvae. The genes related to Ca2+ transport (e.g. plasma membrane Ca2+-ATPase isoform 2, pmca2; Ca2+-ATPase isoform 2, atp2b1a) and regulation (e.g. parathyroid hormone ligand type-1, pth1; stanniocalcin isoform 1, stc1) were significantly downregulated. However, the adverse effects of Cd2+ on otoliths growth and swimming activity can be protected by supplementation of Ca2+ in exposure medium. Body burden of Cd2+ in larvae was reduced upon the supplement with Ca2+. The overall results suggest that exposure to Cd2+ can inhibit influx of Ca2+, leading to less deposition of CaCO3 for otolith growth, and finally result in impaired balance control and swimming activity in zebrafish larvae.

TiO2 nanoparticles and BPA are combined to impair the development of offspring zebrafish after parental coexposure.

Titanium dioxide (TiO2) nanoparticles and bisphenol A (BPA) in aquatic environments interact reciprocally to enhance the maternal transfer of pollutants to offspring, thus varying the innate toxicities during early embryonic development. However, it remains unexplored regarding the molecular mechanisms of developmental toxicity in offspring after parental coexposure. In the present study, adult zebrafish were exposed to TiO2 nanoparticles (100 µg/L), BPA (20 µg/L) or their binary mixture for four months. Then, eggs of F1 generation were collected and reared in clean water until 5 days post-fertilization. In characteristic of larval survival and growth, parental coexposure to TiO2 particles and BPA caused a severer inhibition of F1 offspring larvae compared with single exposure. Mechanistic investigation by shotgun proteomics found that development of larval offspring from coexposed parents was impaired through a distinct mode of toxicity, that is, specifically altering the activity of phagosome and lysosome. Single exposure of adult zebrafish to TiO2 mainly affected insulin-responsive compartment; and BPA parental exposure mainly affected carbohydrate metabolism and calcium signaling of larval offspring. Furthermore, considering the tight regulation of sex hormones in the expression of vitellogenin (VTG), addition of nanoparticles during parental exposure led to inconsistencies between VTG induction and endogenous levels of sex hormones (estradiol and testosterone) in F1 offspring fish. This implied that transfer of nanoparticles to offspring larvae may change the availability of hormonal molecules and BPA at target tissues. Overall, current results provided mechanistic clues into the multigenerational developmental toxicity by parental coexposure to TiO2 particles and BPA.

Endocrine disruption in Chinese rare minnow (Gobiocypris rarus) after long-term exposure to low environmental concentrations of progestin megestrol acetate.

Synthetic progestins are widely used pharmaceutical agents that have become common contaminants in the aquatic environment. The potential adverse effects of long-term exposure on aquatic wildlife, however, are not fully understood. The aim of this study was to investigate the endocrine disruption in Chinese rare minnow (Gobiocypris rarus) in response to megestrol acetate (MTA) exposure. Newly-hatched Chinese rare minnow larvae were exposed to MTA at a nominal concentration of either 1 ng/L (detected concentrations ranged from 0.18 to 0.93 ng/L) or 10 ng/L (detected concentrations ranged from 4.27 to 9.64 ng/L) for 6 months and the effects on growth, sex steroid hormones, gonadal histology, and steroidogenic genes expression were determined. After 6 months of exposure to a nominal concentration of 10 ng/L MTA, the body weight and condition factors were significantly increased in fish of both sexes. Exposure to a nominal concentration of 10 ng/L MTA significantly reduced plasma concentrations of estradiol and 11-ketotestosterone in female fish while also reducing testosterone and 11-ketotestosterone in male fish. Gonad histology revealed significantly reduced proportions of vitellogenic oocytes in female fish exposed to a nominal concentration of 10 ng/L MTA and induction of atretic follicles in female fish exposed to both nominal concentrations of MTA. The expression of cyp19a1a and cyp17a1 in the gonads was up-regulated in the ovaries while down-regulated in the testes. Our results indicate that MTA can induce endocrine disruption in Chinese rare minnow at the low concentrations found in contaminated environments. This indicates a potentially high ecological risk from MTA to fish populations in MTA-contaminated aquatic environments in China and may also in other regions.

Genome-wide identification of 99 autophagy-related (Atg) genes in the monogonont rotifer Brachionus spp. and transcriptional modulation in response to cadmium.

Autophagy originated from the common ancestor of all life forms, and its function is highly conserved from yeast to humans. Autophagy plays a key role in various fundamental biological processes including defense, and has developed through serial interactions of multiple gene sets referred to as autophagy-related (Atg) genes. Despite their significance in metazoan life and evolution, few studies have been conducted to identify these genes in aquatic invertebrates. In this study, we identified whole Atg genes in four Brachionus rotifer spp., namely B. calyciflorus, B. koreanus, B. plicatilis, and B. rotundiformis, through searches of their entire genomes; and we annotated them according to the yeast nomenclature. Twenty-four genes orthologous to yeast genes were present in all of the Brachionus spp. while three additional gene duplicates were identified in the genome of B. koreanus, indicating that these genes had diversified during the speciation. Also, their transcriptional responses to cadmium exposure indicated regulation by cadmium-induced oxidative-stress-related signaling pathways. This study provides valuable information on 99 conserved Atg genes involved in autophagosome formation in Brachionus spp., with transcriptional modulation in response to cadmium, in the context of the role of autophagy in the damage response.

Dysregulation of Intestinal Health by Environmental Pollutants: Involvement of the Estrogen Receptor and Aryl Hydrocarbon Receptor.

To determine how environmental pollutants induce dysbiosis of the gut microbiota, we exposed adult zebrafish to model pollutants with varied modes of action (atrazine, estradiol, polychlorinated biphenyl [PCB]126, and PCB153) for 7 days. Subsequently, metagenomic sequencing of the intestines was performed to compare the gut microbiomes among the groups. We observed clear compound- and sex-specific responses to xenobiotic stress. Principal component analysis revealed involvement of the aryl hydrocarbon receptor (AhR) and, to a lesser extent, the estrogen receptor (ER) in the dysregulation of the intestinal microbiota. The model pollutants differentially impaired intestinal and hepatic physiological activities, as indicated by assessments of gut motility, epithelial permeability, inflammation, and oxidative stress. Correlation analysis showed that abnormal Aeromonas reproduction, especially in the PCB126 groups, was significantly positively associated with oxidative damage. Aeromonas closely interacted with Mannheimia and Blastococcus to regulate intestinal permeability. In summary, we demonstrated that ER and AhR signaling regulated the dynamics of the gut microbiota. Our findings provide new mechanistic insight into the complex interactions between the host metabolism and gut microbiota, which may contribute to the grouped assessment of environmental pollutants in future.

The reproductive responses of earthworms (Eisenia fetida) exposed to nanoscale zero-valent iron (nZVI) in the presence of decabromodiphenyl ether (BDE209).

Reproductive toxicity of nanoscale zero-valent iron (nZVI) along with coexisting decabromodiphenyl ether (BDE209) to earthworm Eisenia fetida (E. fetida) remains unknown. In the present study, the reproductive responses of E. fetida exposed to 100, 500 and 1000 mg kg-1 of nZVI showed a significant (P < 0.05) decline up to 35.6%, 60.0% and 93.3%, respectively, compared to the controls. Expression levels of annetocin (ANN) gene indicated a remarkable (P < 0.05) down-regulation (59.2%, 58.2% and 95.0%, correspondingly), and it was positively correlated with reproductive rates (R = 0.94). Iron contents in E. fetida were also relevant to reproductive behavior (R = 0.84) and ANN expression (R = 0.75). Additionally, seminal vesicles displayed a progressive degeneration with increasing nZVI levels. The addition of BDE209 to low level of nZVI-polluted group (100 mg kg-1 dw) barely caused clear changes on reproduction, histopathology and ANN, while the coexistence resulted in significant impacts in comparison with high level of single nZVI exposure (1000 mg kg-1 dw). These observations would provide some significant information concerning joint toxicity of the two chemicals in a soil system.

Toxic responses of microorganisms to nickel exposure in farmland soil in the presence of earthworm (Eisenia fetida).

Nickel (Ni)-contamination impairs soil ecosystem, threatening human health. A laboratory simulation of Ni-polluted farmland soil study, in the presence or absence of earthworm, was carried out to investigate the toxic responses of soil microorganisms, including microbial biomass C (MBC), soil basal respiration (SBR), metabolic quotient (qCO2), urease (UA) and dehydrogenase activities (DHA). Additionally, the variations of Ni bioavailability were also explored. Results manifested that MBC and SBR were stimulated at 50 and 100 mg·kg-1 of Ni but inhibited by further increasing Ni level, showing a Hormesis effect. Earthworm input delayed the occurrence of a maximum SBR inhibition rate under the combined double-factors of time and dose. No specific effect of Ni concentration on the qCO2 was observed. UA was significantly suppressed at 800 mg·kg-1 Ni (P < 0.05 or 0.01), whereas DHA was more sensitive and significantly inhibited throughout all the treatments (P < 0.01), indicating a pronounced dose-response relationship. The addition of earthworm facilitated all the biomarkers above. The time-dependent of dose-effect relationship (TDR) on MBC and SBR inhibition rates suggested that the peak responsiveness of microorganisms to Ni stress were approximate on the 21st day. The bioavailable form of per unit Ni concentration declined with time expanded and concentration increased, and the changeable process of the relative amount of bioavailability was mainly controlled by a physicochemical reactions.

Editor's Highlight: Structure-Based Investigation on the Binding and Activation of Typical Pesticides With Thyroid Receptor.

A broad range of pesticides have been reported to interfere with the normal function of the thyroid endocrine system. However, the precise mechanism(s) of action has not yet been thoroughly elucidated. In this study, 21 pesticides were assessed for their binding interactions and the potential to disrupt thyroid homeostasis. In the GH3 luciferase reporter gene assays, 5 of the pesticides tested had agonistic effects in the order of procymidone > imidacloprid > mancozeb > fluroxypyr > atrazine. 11 pesticides inhibited luciferase activity of T3 to varying degrees, demonstrating their antagonistic activity. And there are 4 pesticides showed mixed effects when treated with different concentrations. Surface plasmon resonance (SPR) biosensor technique was used to directly measure the binding interactions of these pesticides to the human thyroid hormone receptor (hTR). 13 pesticides were observed to bind directly with TR, with a KD ranging from 4.80E-08 M to 9.44E-07 M. The association and disassociation of the hTR/pesticide complex revealed 2 distinctive binding modes between the agonists and antagonists. At the same time, a different binding mode was displayed by the pesticides showed mix agonist and antagonist activity. In addition, the molecular docking simulation analyses indicated that the interaction energy calculated by CDOCKER for the agonists and antagonists correlated well with the KD values measured by the surface plasmon resonance assay. These results help to explain the differences of the TR activities of these tested pesticides.

Transgenerational endocrine disruption and neurotoxicity in zebrafish larvae after parental exposure to binary mixtures of decabromodiphenyl ether (BDE-209) and lead.

Polybrominated diphenyl ethers (PBDEs) and heavy metals are two key groups of electric and electronic equipment contaminants. Despite their co-occurrence in aquatic environments, their combined effects remain largely unknown, particularly under a chronic exposure regime. In the present study, adult zebrafish (Danio rerio) were exposed to environmentally relevant concentrations of BDE-209 and lead (Pb), or their binary mixtures, for 3 months. After chronic parental exposure, increased transfer of BDE-209 and Pb to the offspring eggs was activated in the coexposure groups, with BDE-197 being the predominant PBDE congener, indicating the dynamic metabolism of BDE-209 in parental zebrafish. In the presence of Pb, culturing the eggs in clean water until 5 days post-fertilization (dpf) further accelerated the debromination of BDE-209 towards BDE-197 in the offspring, caused by the preferential removal of bromine atoms at meta positions. BDE-209 and Pb combinations induced reproductive and thyroid endocrine disruption in adults, which resulted in an imbalanced deposition of hormones in the eggs. However, compared with single chemical exposure, the larval offspring at 5 dpf from the coexposure groups had reversed the adverse influences from maternal origin. In addition, the interaction between BDE-209 and Pb led to transgenerational developmental neurotoxicity in the larval offspring, where inhibited neuronal growth and neurotransmitter signaling, disorganized muscular assembly, and impaired visual function contributed to the observed neurobehavioral deficits. Overall, depending on specific biological events, the complex interaction between BDE-209 and Pb under chronic exposure resulted in significant alterations in their environmental fate and toxicological actions, thus complicating the accurate evaluation of ecological risks and constituting an unquantified threat to environmental safety.

The involvement of autophagy and cytoskeletal regulation in TDCIPP-induced SH-SY5Y cell differentiation.

Exposure and toxicity to organophosphate-based flame retardants are an increasing health concern. Neurons appear to be particularly vulnerable to the effects of these chemicals. For example, in vitro studies have shown that tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) induces apoptosis and autophagy in neural cells. In the present study, we investigated the cell biological mechanisms of TDCIPP-induced neurotoxicity using undifferentiated human SH-SY5Y neuroblastoma cells as a model. Interestingly, TDCIPP treatment promoted differentiation in SH-SY5Y cells, which displayed various alterations including neurite elongation, an expansion of the numbers of neurite-bearing cells, and an increase in expression of cytoskeletal components normally enriched in neurons. Furthermore, the upregulation of microtubule-associated protein light chain 3, the degradation of p62/sequestosome 1, and the formation of autophagosomes occurred in treated cells, suggesting that TDCIPP exposure induces autophagy. However, pretreatment with the autophagy inhibitor 3-methyladenine suppressed TDCIPP-induced autophagy and reduced expression of the aforementioned cytoskeletal components. This correlated with a reduction in neurite outgrowth and numbers of neurite-bearing cells. Taken together, these results indicate that autophagy might promote TDCIPP-induced SH-SY5Y cell differentiation, which leads to an increase in expression of cytoskeletal components and neurite outgrowth. This study offers key insights into the mechanisms of neurotoxicity associated with this commonly used organophosphate.

Occurrence and Characteristics of Microplastic Pollution in Xiangxi Bay of Three Gorges Reservoir, China.

Microplastic pollution in inland waters is receiving growing attentions. Reservoirs are suspected to be particularly vulnerable to microplastic pollution. However, very limited information is currently available on pollution characteristics of microplastics in reservoir ecosystems. This work studied the distribution and characteristics of microplastics in the backwater area of Xiangxi River, a typical tributary of the Three Gorges Reservoir. Microplastics were detected in both surface water and sediment with concentrations ranging from 0.55 × 105 to 342 × 105 items km-2 and 80 to 864 items m-2, respectively. Polyethylene, polypropylene, and polystyrene were identified in surface water, whereas polyethylene, polypropylene, and polyethylene terephthalate, and pigments were observed in sediment. In addition, microplastics were also detected in the digestion tracts of 25.7% of fish samples, and polyethylene and nylon were identified. Redundancy analysis indicates a weak correlation between microplastics and water quality variables but a negative correlation with water level of the reservoir and Secchi depth. Results from this study confirm the presence of high abundance microplastics in reservoir impacted tributaries, and suggest that water level regulated hydrodynamic condition and input of nonpoint sources are important regulators for microplastic accumulation and distribution in the backwater area of reservoir tributaries.

Linking genomic responses of gonads with reproductive impairment in marine medaka (Oryzias melastigma) exposed chronically to the chemopreventive and antifouling agent, 3,3'-diindolylmethane (DIM).

3,3'-Diindolylmethane (DIM) has been promoted as an effective chemopreventive and antifouling additive. However, the concurrent risks or side effects of DIM are not fully understood, especially on tissues responsive to estrogen. Therefore, this study employed marine medaka (Oryzias melastigma) as a test model to evaluate relative safety and explore mechanisms of toxic action of DIM on development and function of gonad after chronic (28days) aqueous exposure to relatively low doses (0µg/L or 8.5µg/L). Integration of comprehensive toxicogenomic analysis at the transcriptome and proteome levels with apical endpoints, such as production of eggs and swimming performance of larvae, elucidated the molecular linkage in gonad from bottom up along the reproductive adverse outcome pathway. A series of sequential changes at the transcript and protein levels were linked to lesser fecundity and viability of larvae exposed to DIM. Anomalous production of vitellogenin (VTG) and eggshell proteins in testis confirmed the estrogenic potency of DIM. In the ovary, although storage of VTG was greater, lesser expressions of cathepsin enzymes blocked cleavage and incorporation of VTG into oocytes as yolk, which acted together with lower eggshell proteins to inhibit maturation of primary oocyte and thus contributed to impairment of fecundity. Overall, this study demonstrated that exposure to DIM impaired reproductive fitness. Diverse molecular initiating changes in gonads were linked to apical endpoints that could be used in assessment of risks posed by DIM on gametogenesis. In combination with chemical stability and potent endocrine disruption, the results of this study can inform decisions about the use of DIM either as chemopreventive or antifouling agent.

Tris (1,3-dichloro-2-propyl) phosphate-induced apoptotic signaling pathways in SH-SY5Y neuroblastoma cells.

Tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP, also known as TDCPP), an extensively used flame retardant, is frequently detected in the environment and biota. Recent studies have shown that TDCIPP has neurotoxic effects. In this study, we determined the mechanisms of TDCIPP-induced neurotoxicity in human neuroblastoma (SH-SY5Y) cells. By using morphological examination, flow cytometry, and mitochondrial membrane potential (ΔYm) measurement, we confirmed that exposure to TDCIPP caused apoptosis accompanied by the activation of apoptosis-related genes (e.g. Bax and Bcl-2) and caspase 3 protein in SH-SY5Y cells. Increased reactive oxygen species (ROS) formation and intracellular calcium ions ([Ca2+]i) were also observed in TDCIPP-treated SH-SY5Y cells. Exposure to TDCIPP led to the activation of protein markers of endoplasmic reticulum (ER) stress, including eukaryotic translation initiation factor 2a subunit (p-EIF2a), activation transcription factor (ATF4), glucose-regulated protein (GRP78), and the proapoptotic factor C/EBP homologous protein (CHOP). To determine the role of the ER in apoptosis, phenyl butyric acid (PBA), an ER stress inhibitor, was applied. Treatment with PBA effectively attenuated TDCIPP-induced ER stress and protected against apoptotic death in SH-SY5Y cells by inhibition of Bax expression and promotion of Bcl-2 expression. Furthermore, we found that pretreatment of the cells with the ROS scavenger N-acetyl cysteine (NAC) inhibited the ER stress response and prevented apoptosis. The combination of PBA and NAC pretreatment could further prevent TDCIPP induced ER-stress and apoptotic death compared with PBA or NAC pretreatment alone. Thus, in the present study, we demonstrated that TDCIPP induces cytotoxicity through a ROS-dependent mechanism involving ER stress and activation of mitochondrial apoptotic pathways in SH-SY5Y cells.

Genome-wide identification of ATP-binding cassette (ABC) transporters and conservation of their xenobiotic transporter function in the monogonont rotifer (Brachionus koreanus).

The ATP-binding cassette (ABC) transporter family is one of the largest gene family in animals, and members of this family are known to be involved in various biological processes due to their ability to transport a wide range of substrates across membranes using ATP cleavage-derived energy. We identified 61 ABC transporters in the genome of the monogonont rotifer Brachionus koreanus, and classified these into eight distinct subfamilies (A-H) by phylogenetic analysis. ABC transporters in the rotifer B. koreanus are comprised of 11 ABCA genes, 19 ABCB genes, 14 ABCC genes, 3 ABCD genes, 1 ABCE gene, 3 ABCF genes, 8 ABCG genes, and 2 ABCH genes. Extensive gene duplication and loss events in synteny were observed in several subfamilies. In particular, massive gene duplications of P-glycoproteins (P-gps), multidrug resistance proteins (MRPs), and Bk-Abcg-like proteins were observed. The ability of these B. koreanus proteins to function as multixenobiotic resistance (MXR) ABC transporters was validated using specific fluorescence substrates/inhibitors. The ABC transporter superfamily members identified in this study will be useful in future toxicological studies, and will facilitate comparative studies of the evolution of the ABC transporter superfamily in invertebrates.